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Topic: IM vs Scale Trains speakers (Read 355 times)

I was prodding around in my IM SD40-2 and Scale Trains C39-8 and noticed they both use similar 15x11 speakers. The IM has a VERY slim enclosure. I think it might be possible to use an enclosure from this (or a similar one scratch built) to fix the ongoing sound issues on the ST engines.

Anyone tried playing around with their ST C39-8 or T-4 speakers?

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I was digging around in my c39-8 too. It’s a dc one that I fitted a lokpilot next 18.The way I see it is enclosing the 11 x 15 speaker in the ST will help but it can’t fire up into the shell from the tank as the frame is solid metal with a small hole for speaker wires only.The IM deuce is split frame so the sound can get up into the shell. Enclosure volume would be way small too. But an 8 x 12 speaker in a 11 x 16 x 3.5mm enclosure would give about 525mm3 which is the sweet spot for those speakers and fire it down through the tank might be a solution.

Would be interested on your findings and thoughts as this loco really does deserve to have great sound.

I’m still head scratching this as I also have a couple of dc ST dash 9’s on pre-order which I will want to put sound in.Am Assuming the speaker set up will be the same or very similar to the c39-8.

Another idea I’ve just had is to not make an enclosure in the usual way but glue strips of styrene to the edges of the 11x15 or even a 9x16 speaker to both widen and lengthen the speaker and shape these additional strips to be a snug fit in the tank opening. Maybe glue a couple of rest strips in the tank recess so you don’t push it in too far as well.Then Drill a few holes in the tank bottom for the sound to come out. This way you just have to seal up the small hole with silicone or similar after the speaker wires are threaded through the frame and similarly seal the snug fitting speaker to edges of the tank recess such that the diaphragm is level with the tank/frame bottom. This would maximize the enclosed volume to around 750mm3. The sweet spot for a 9x16mm and just in the ball park for the the 11 x 15 too.

I’m still head scratching this as I also have a couple of dc ST dash 9’s on pre-order which I will want to put sound in.Am Assuming the speaker set up will be the same or very similar to the c39-8.

Another idea I’ve just had is to not make an enclosure in the usual way but glue strips of styrene to the edges of the 11x15 or even a 9x16 speaker to both widen and lengthen the speaker and shape these additional strips to be a snug fit in the tank opening. Maybe glue a couple of rest strips in the tank recess so you don’t push it in too far as well.Then Drill a few holes in the tank bottom for the sound to come out. This way you just have to seal up the small hole with silicone or similar after the speaker wires are threaded through the frame and similarly seal the snug fitting speaker to edges of the tank recess such that the diaphragm is level with the tank/frame bottom. This would maximize the enclosed volume to around 750mm3. The sweet spot for a 9x16mm and just in the ball park for the the 11 x 15 too.

Any thoughts on this ?

You're on the same wave length af me. I was thinking of using the cavity as the enclosure and have the speaker "fire" towards the track with some porting through the fuel tank.

You're on the same wave length af me. I was thinking of using the cavity as the enclosure and have the speaker "fire" towards the track with some porting through the fuel tank.

Great 👍. Let us know how it works out. Maybe a before and after video too perhaps. I have to wait till the summer for my dash 9’s to try it.Of course if you ditched the OEM dc board with next 18 connector you could go the traditional root with a speaker aft and decoder fwd and with a roll your own pcb with resistors etc etc in the middle on top and caps or extra weight in the tank. But that’s a hell of a lot of work especially on a brand new loco.

I been shopping around Digikey for possible solutions to the anemic Scale Trains speaker.

One of the ones I purchased is this PUI 11x15 with an adhesive mount. The cool thing about this speaker is that it has a bit of depth to it while still fitting the C39-8 housing. It may not be as good as a custom enclosure, but it might provide better range. I'll be testing this with a stationary decoder before having into my new engines.

That is not an airtight enclosure - it just adds thickness on the top of the speaker. So I imagine that you are planning on sticking it to some flat surface (to create an airtight chamber)? It is awfully small, but better than an open speaker.

That's the plan. I have to see if I can mount it to the fuel tank. One of the interesting things I found with the ST engines is that the speaker's metal plate faces down, which is opposite IM and Atlas. I'm not sure if that has any negative effect. I don't believe that the ST speaker is fully sealed.

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You've crossed the walls, excelled Further along through their hell All for my heart, I watch you kill You always have, you always will Now spread your wings and sail out to me

Well, I hate to say it, but what I'd do is mill a larger opening in the fuel tank area, and then use one of John LeMerise's offset enclosures for a 9x16mm speaker in an IM SD40-2. The fuel tank area overall looks huge - at least as big as the SD40-2 tank. So if you could mill out enough space, you could use this enclosure with a 9x16 speaker:

Yep but making an enclosure around the speaker will take up volume which is pretty marginal as is. What I’m thinking and in order to avoid milling out the tank area and still get max volume for an enclosure is to glue some strip styrene the same depth as the speaker case (about 2mm) to all sides of a 16 x 9 speaker to get the speaker outside dimensions to 17mm x 11.5mm. Shape the corners of the enlarged speaker case to fit the frame tank recess (these are radiused) such that the now enlarged speaker case will press fit into the tank recess with the speaker diaphragm facing down and it’s face flush with the bottom of the frame. Once speaker is in and sealed to the frame, Port the tank cover to let the sound out. You would have to seal off the small hole in the bottom of the solid frame in way of the tank recess where the wires would go upto the decoder with silicone or similar after threading the speaker wires through.In this way the tank recess would then be the speaker enclosure and be 17 x 11.5 x 4mm giving 782mm3 enclosure volume which is pretty much on the money for the 16x9 speaker.You could do similar with a 15x11 speaker too.If you have a milling machine then other options are possible too of course but for those of us that don’t this might be a good way to achieve a better speaker set up on these locos without a lot of effort and skill. Hope my explanation is understandable.